This is how my school doesn't have to have 120 hours for the commercial course. Our commercial courses are approved under 141.55 (d) and (e). See below:
141.55 Training course: Contents
(d) A pilot school may request and receive initial approval for a period of not more than 24 calendar months for any of the training courses of this part without specifying the minimum ground and flight training time requirements of this part, provided the following provisions are met:
(1) The school holds a pilot school certificate issued under this part and has held that certificate for a period of at least 24 consecutive calendar months preceding the month of the request;
(2) In addition to the information required by paragraph (c) of this section, the training course specifies planned ground and flight training time requirements for the course (this is specific to the FSDO approved course) ;
(3) The school does not request the training course to be approved for examining authority, nor may that school hold examining authority for that course; and
(4) The practical test or knowledge test for the course is to be given by--
(i) An FAA inspector; or
(ii) An examiner who is not an employee of the school.
(e) A certificated pilot school may request and receive final approval for any of the training courses of this part without specifying the minimum ground and flight training time requirements of this part, provided the following conditions are met:
(1) The school has held initial approval for that training course for at least 24 calendar months.
(2) The school has--
(i) Trained at least 10 students in that training course within the preceding 24 calendar months and recommended those students for a pilot, flight instructor, or ground instructor certificate or rating; and
(ii) At least 80 percent of those students passed the practical or knowledge test, or any combination thereof, on the first attempt, and that test was given by--
(A) An FAA inspector; or
(B) An examiner who is not an employee of the school.
(3) In addition to the information required by paragraph (c) of this section, the training course specifies planned ground and flight training time requirements for the course.
(4) The school does not request that the training course be approved for examining authority nor may that school hold examining authority for that course.
END OF REGULATION
Our course requires less than 30 hours of dual for the commercial rating. However, this is an absolute minimum and is very difficult to come by. I hope this answers the question you had above. Again, it would be best to consult with the specific school to find out whether or not they are approved under part 141.55 (d) and (e). If they are, this could reduce your costs considerably since appendix D states the following:
141 Appendix D, section:
4. Flight training. (a) Each approved course must include at least the following flight training, as provided in this section and section No. 5 of this appendix, on the approved areas of operation listed in paragraph (d) of this section that are appropriate to the aircraft category and class rating for which the course applies:
(1) 120 hours of training if the course is for an airplane or powered-lift rating.
Good luck!